Prior art oligosaccharide-like amylase inhibitors, Nojirimycin [Agr. Biol. Chem., 34, 966(1970)], S-AI(Amylostatin) [U.S. Pat. No. 4,010,258], NCGAI [Japanese Pat. Laying-Open No. 54,990/76, Japanese Patent Publication No. 24119/77], and the aminosugar derivatives by Frommer et al [U.S. Pat. No. 4,062,950].
The novel oligosaccharide-like amylase inhibitors of this invention, TAI-A and TAI-B, are distinguished from Nojirimycin in terms of lack of their inhibitory activity to .alpha.-glucosidase, from S-AI in terms of their adsorption to acidic and basic ion exchange resins and lack of their inhibitory activity to bacterial liquefying .alpha.-amylase, from NCGAI in terms of their optical activity and lack of their inhibitory activity to bacterial liquefying .alpha.-amylase, and from the aminosugar derivatives of Frommer et al in terms of lack of methyl groups in their molecules.